Gas pressure alarm system for cables



S. P. SHACKLETON GAS PRESSURE ALARM SYSTEM FOR CABLES Filed May 28, 1942April 1l, 1944.

Patented Apr. il, 1944 GS PRESSURE ALARM SYSTEM FOR CABLES Samuel E.Shackleton, Maplewood, N. J., assigner to Bell Telephone Laboratories,Incorporated, New York, N. Y., a corporation of New York Applicationleay 28, 1942, Serial No. 444,813

1) Claims.

This invention relates to indicating means and more particularly toarrangements of apparatus 'and circuits for indicating at which one of anumber of xed points a pair of conductors has been short-circuited.

Long cables, particularly toll cables, are frequently kept under gaspressure to prevent the entrance of moisture into the cables and topermit the rapid location of sheath openings before the occurrence ofinsulation trouble. Leakage through the cable sheath causes a reductionin gas pressure which may be detected by means of a contact makingpressure gauge such as disclosed in United States Patent 1,984,226granted April 18, 1933, to T. C. Henneberger and 1,936,194 grantedNovember 21, 1933, to T. C. Henneberger and V. B. Pike. A rapid meansfor determining the exact location of the contact making pressure gaugewhich has operated is shown by United States patents, 1,855,321 grantedApril 26, 1932, to S. P. Shackleton and 1,904,227 granted April 18,1933, to T. C. Henneberger- Experience has shown that for cable sectionslonger than fty miles false alarms may be troublesome and in the eventof a magnetic storm the gas pressure alarms may be rendered inoperative.In the operation of such systems it is desirable to have attendedoffices two hundred miles or more apart with a series of intermediateunattended oihces distributed therebetween. In order to successfullyoperate such a system it is essential that some means be provided forlocally detecting gas pressure failures over lengths of cable notgreater than fifty miles and for relaying them on to one of the adjacentattended oflices.

It is therefore the object of this invention to provide a switchingarrangement for toll cable gas pressure alarm systems to permit anunattended oihce to transfer its alarm signal to an adjacent attendedoffice.

The foregoing object is attained by this invention which provides aswitching system comprising in combination an alarm system for eachcable section responsive to the operation of its own short-circuitingdevices, a magnetic switch for each alarm system the operation whereofis adapted to disconnect the bridged conductors of its associated cablesection from its own alarm system and connect them to the bridgedconductors in an adjacent cable section, a circuit means included witheach alarm system for operating its associated magnetic switch inresponse to the operation of the alarm system, and a locking circuit forlocking the magnetic switch in its operated position.

The invention may be better understood by referring to the accompanyingdrawing in which:

Fig. 1 shows a schematic of a complete system in accordance with thisinvention; and

Fig. 2 shows the detailed circuit of one of the normally unattendedrepeater stations.

Referring now more particularly to Fig. 1 in which there is shown twoattended repeater stations referred to as oice A and oiiice D; disposedbetween attended oflices A and D are unattended oices B and C. All ofthese offices, A, B, C and D are interconnected by a series oi cablesections AB, BC, and CD. While only two intermediate unattended oiilcesare shown it is obvious that the invention is not limited to that numberbut that any number of such oices may be used. Each of theinterconnecting cable sections contains a large number of conductorpairs and one of these pairs is bridged with a plurality of pressureresponsive contactors 2. For illustrative purposes each of these cablesections shows only two of these pressure responsive contactors.However, in actual practice many more are actually used and spaced atfrequent intervals along the length of each cable section.

It will be understood that upon the operation of any one of thesepressure responsive contactors 2, for example, contactor 2 in cablesection BC, the alarm circuit at the rst oflice to the right will becaused to operate. In accordance with this invention if the cnice to theright is attended the alarm goes no further. However, in the event theolice is unattended circuits will be set up to cause magnetic switch 3to operate and transfer the shorted indication through the bridgedconductcrs of the next intermediate cable section to the second oce tothe right. If this oilice is also unattended the process will be againrepeated until the shorted condition reaches an attended oilicewhereupon the alarm will be received in the usual manner and located bythe circuits and methods shown in the patents mentioned above.

As previously stated, pressure responsive contactor 2' of cable sectionBC is shown closed thereby placing a short across their cable pair I.This caused the operation of the local alarm circuit in oiiice C whichis the rst oihce to the right. Since this is a normally unattendedstation, the local alarm circuit operated in a manner to be moreparticularly described in connection with Fig. 2 with the result thatmagnetic switch 3 in oflice C has operated as shown in Fig. 1 totransfer the short through the conductor pair l of cable section CD tothe attended office D.

Referring now to Fig. 2 it will be seen in detail how the circuits ofthis invention cause this transfer to take place. In Fig. 1 it wasassumed that pressure responsive contactor 2' had operated and that thishad ultimately caused the operation of magnetic switch 3 in oiiice C. InFig. 2 it is assumed that pressure responsive contactor 2' has not yetoperated and that oiiice C which is normally unattended is at presentattended. While this oiiice remains attended key 'l is left open so thatmagnetic switch 3 is unable to operate. This causes oice C to operate insubstantially the same manner as any ordinary attended oice. Upon theoperation of pressure responsive contactor 2 an obvious circuit iscompleted through the back contacts of magnetic switch 3 and through thecoil of the detector relay causing this relay to operate and close itscontacts. The operation of the detector relay completes an obviouscircuit through the coil of the alarm relay causing both its contacts IBand H to close. Contacts I merely place ground on one terminal of thecoil of magnetic switch 3 but since key 'l is open the coil is notenergized. Contacts Il of the alarm relay close a local circuit throughthe cnice alarm and the procedure thereaiterfor locating the pressureresponsive contactor which is operated may be substantially the same asthat shown in the two above-mentioned patents, 1,855,321 and 1,904,227.

Now let it be assumed that the oiice is to be left unattended which, inaccordance with this invention, is the intended normal operation of thisoiiice. Before leaving the ofiice the attendant closes key 1. It willthus be seen that upon the operation of one of the pressure responsivecontactors for example contactor 2 in cable section BC the detectorrelay in office C will be caused to operate as before which results alsoin the operation of the alarm relay and the oilce alarm. In this case,however, a circuit is completed from ground through contacts l0 of thealarm relay, through the coil of the magnetic switch, through keyresistor 8, battery 9 and back to ground, thereby causing the operationof magnetic switch 3. Magnetic switch 3 is locked in its operatedposition through its contact 6 which maintains ground on the oneterminal of its coil. Also upon the operation of magnetic switch 3 theshorted condition produced by pressure responsive contactor 2' isremoved from the detector relay causing its release along with therelease of the alarm relay, thereby silencing the ofce alarm.v Theoperation of magnetic switch 3 also causes a transfer of the shortedcondition in cable section BC to conductor pair l in cable section CDthrough an obvio-us circuit including the front contacts of magneticswitch 3. This is the condition which is indicated at oiice C in Fig. 1.It will be understood that this shorted condition thus transferred toconductor pair I of cable section CD will cause the operation of thealarm circuit in attended oilice D as previously stated.

The attendant at cnice D tests for the location of the operated pressureresponsive contactor in the manner disclosed in either of the twoabovementioned patents. Having completed this test he closes key i shownin the block for cnice D in Fig. l. This places ground on conductorwhich is carried through all of the cable sections to all of thenormally unattended oiiices to the left of cnice D. Referring now toFig. 2 it will be seen fill that upon placing ground on conductor 5 itcauses the operation of the restoring relay through an obvious circuitcarried from ground through conductor 5 through the coil of therestoring relay, its associated battery and ground. Since one side ofthe coil of magnetic switch 3 is already grounded' through itsinterlocking contact 6, this coil is short-circuited by reason of theoperation of the restoring relay, the current from battery 9 beingcarried through resistor 8, key 1, the contacts of the restoring relayand back to ground. This causes the release of all of the magneticswitches 3 of all of the normally unattended ofces which have beenaffected by the closure of one of the pressure responsive contactors 2.

Of course, it will be understood that if the shorted condition stillexists after the operation of the restoring relay, that immediately uponreleasing key 4 in the attended station, the alarm circuits and transferconditions previously described will repeat themselves and the alarm inolice C will again be operated. However, upon repairing the fault andrestoring the gas pressure in the faulty cable section, the operation ofkey 4 in the attended oilice C will restore the sectionalized operationof the complete alarm system.

Referring now to the above noted faulty operation during a magneticstorm, it will be observed that with the circuits of this inventionthere will be at no time an alarm pair longer 'than one cable sectionstanding open to permit the building up of excessive induced voltages.Until an alarm occurs the alarm pairs in the single sections will standopen and connected to their individual alarm circuits. These shorter,sectionalized circuits are not susceptible to the trouble duringmagnetic storms which has been experienced with longer alarm circuits.When an alarm does occur only those sections are connected togetherwhich are required to actuate the alarm at the attended office.

What is claimed is:

l. A switching means for an alarm circuit in a cable system of the typehaving a plurality of series-coupled cable sections, said switchingmeans comprising for each cable section, a pair of conductors bridged byshort-circuiting devices, a two-pole magnetic switch, front and backcontacts for each pole, circuits connecting said two poles to the pairof bridged conductors of their associated cable section, a relay means,circuits connecting the back contacts to the relay means whereby saidrelay means is responsive to the operation of any of theshort-circuiting devices of said associated cable section, circuitsconnecting said front contacts to the pair of bridged conductors of theadjacent cable section, an energizing circuit for said magnetic switchconnected to said relay means and responsive to the operation thereof,whereby upon the operation of said magnetic switch the bridgedconductors of the associated cable section may be disconnected from saidrelay means land connected to the bridged conductors of said adjacentcable section, and a locking circuit including contacts on said magneticswitch connected to said energizing circuit for locking the magneticswitch in its operated position.

2. A switching means for an alarm circuit in a cable system of the typehaving a plurality of series-coupled cable sections, said switchingmeans comprising for each cable section, a pair of conductors bridged byshort-circuiting devices, a two-pole magnetic switch, front and backcon-` tacts for each pole, circuits connecting said two poles to thepair of bridged conductors of their associated cable section, a relaymeans, circuits connecting the back contacts to the relay means wherebysaid relay means is responsive to the operation of any of theshort-circuiting devices of said associated cable section, circuitsconnecting said front contacts to the pair of bridged conductors of theadjacent cable section, an energizing circuit for said magnetic switchconnected to said relay means and responsive to the operation thereof,whereby upon the operation of said magnetic switch the bridgedconductors of the associated cable section may be disconnected from saidrelay means and connected to the bridged conductors of said adjacentcable section, a locking circuit including contacts on said magneticswitch connected to said energizing circuit for locking the magneticswitch in its operated position, and a circuit connected to saidenergizing circuit for restoring the magnetic switch to its unoperatedposition.

3. A switching means for an alarm circuit in a cable system of the typehaving a plurality of series-coupled cable sections, said switchingmeans comprising for each cable section, a pair of conductors bridged byshort-circuiting devices, a two-pole magnetic switch, front and backcontacts for each pole, circuits connecting said two poles to the pairof bridged conductors of their associated cable section, a relay meansincluding a detector relay and an alarm relay, circuits connecting theback contacts to the detector relay whereby said detector relay isresponsive to the operation of any of the short-circuiting devices ofsaid associated cable section, circuits connecting said front contactsto the pair of bridged conductors of the adjacent cable section,circuits connecting said alarm relay to said detector relay, whereby theoperation of said alarm relay is responsive to the operation of saiddetector relay, an energizing circuit for said magnetic switch connectedto said alarm relay and responsive to the operation thereof, wherebyupon the operation of said magnetic switch the bridged conductors of theassociated cable section may be disconnected from said detector relayand connected to the bridged conductors of said adjacent cable section.

4. A switching means for an alarm circuit in a cable system of the typehaving a plurality of series-coupled cable sections, said switchingmeans comprising for each cable section a pair of conductors bridged byshort-circuiting devices, a two-pole magnetic switch, front and backcontacts for each pole, circuits connecting said two poles to the pairof bridged conductors of their associated cable section, a relay meansincluding a detector relay and an alarm relay, circuits connecting theback contacts to the detector relay whereby said detector relay isresponsive to the operation of any of the short-circuiting devices ofsaid associated cable section, circuits connecting said front contactsto the pair of bridged conductors of the adjacent cable section,circuits connecting said alarm relay to said detector relay, whereby theoperation of said alarm relay is responsive to the operation of saiddetector relay, an energizing circuit for said magnetic switch connectedto said alarm relay and responsive to the operation thereof, wherebyupon the operation of said magnetic switch the bridged conductors of theassociated cable section may be disconnected from said detector relayand connected to the bridged conductors of said adjacent cable section,and a locking circuit including contacts on said magnetic switchconnected to said energizing circuit for locking the magnetic switch inits operated position.

5. A switching means for an alarm circuit in a cable system oi the typehaving a plurality of series coupled cable sections, said switchingmeans comprising for each cable section a pair of conductors bridged byshort-circuiting devices, a two-pole magnetic switch, front and backcontacts for each pole, circuits connecting said two poles to the pairof bridged conductors ci their associated cable section, a relay meansincluding a detector relay and an alarm relay, circuits connecting theback contacts to the detector relay whereby said detector relay isresponsive to the operation of any of the short-circuiting devices ofsaid associated cable section, circuits connecting said front contactsto the pair of bridged conduct-ors of the adjacent cable section,circuits connecting said alarm relay to said detector relay whereby theoperation of said alarm relay is responsive to the operation of saiddetector relay, an energizing circuit for said magnetic switch connectedto the alarm relay and responsive to the operation thereof, whereby uponthe operation of said magnetic switch the bridged conductors of theassociated cable section may be disconnected from said detector relayand connected to the bridged conductors of said adjacent cable section,a locking circuit including contacts on said magnetic switch connectedto said energizing circuit for locking the magnetic switch in itsoperated position, and a circuit connected to said energizing circuitfor restoring the magnetic switch to its unoperated position.

6. The combination of claim 1 and a key in series with said energizingcircuit for rendering the magnetic switch inoperative.

7. The combination of claim 2 and a key in series with said energizingcircuit for rendering the magnetic switch inoperative.

8. The combination of claim 3 and a key in series with said energizingcircuit for rendering the magnetic switch inoperative.

9. The combination of claim 4 and a key in series with said energizingcircuit for rendering the magnetic switch inoperative.

10. The combination of claim 5 and a key in series with said energizingcircuit for rendering the magnetic switch inoperative.

SAMUEL P. SHACKLETON.

